1. Field of the Invention
The present invention generally relates to a method of fabricating a color filter. More particularly, the present invention relates to a method of fabricating a color filter, wherein the possibility of intermixing the color inks in adjacent sub-pixel regions can be substantially reduced.
2. Description of Related Art
As the development of the performance of computer, internet, and multimedia technology, the transformation of image information has gradually progressed from analog information to digital information. In recent years, the size and the weight of electronic devices have been gradually reduced to produce thinner and lighter electronic products. As to a display device, although the conventional cathode ray tube (CRT) display is widely used, however, it has the disadvantages of large size, high radiation, heavy weight and high power consumption. Therefore, the flat panel display (FPD), which has the advantages of being thinner, flatter, lighter, low or radiation free, and low power consumption, has gradually become the mainstream of display devices. The flat panel display (FPD) includes, for example, liquid crystal display (LCD), organic light emitting display (OLED) or plasma display panel (PDP).
A conventional liquid crystal display (LCD) consists mainly of a thin film transistor (TFT) array, a color filter, and a liquid crystal layer disposed between the thin film transistor array and the color filter. The color display of the liquid crystal display is generally performed by color filters. The color filter is generally constructed over a transparent glass substrate. The color filter generally comprises a black matrix and a color filter layer comprising, for example, red filter units, green filter units and blue filter units arranged corresponding to each sub-pixel, wherein the black matrix is adopted for shield light.
A fabrication method for forming a color filter layer by inkjet printing has been developed recently. According to this conventional fabrication method, first, a black matrix is formed on a substrate to define a plurality of sub-pixel regions. An inkjet printing process is then performed to inject a color ink (red, green, or blue) into the sub-pixel regions defined by the black matrix. Next, a thermal baking process may be performed to solidify the color ink.
The above conventional fabrication method, however, has some shortcomings, such as, during the injection of the color ink into the sub-pixel regions between patterns of the black matrix, the level of the color ink in each of sub-pixel areas is often higher than the surface of the black matrix since the volume of the color ink injected is usually a little larger than that defined by the sub-pixel areas. Therefore, the problem of intermixing of the color inks in adjacent sub-pixel regions may occur if the inkjet printing process is not properly controlled.
In order to resolve the above problem, a hydrophobic film is formed on the black matrix before forming the color filtering layer using a plasma process. However, instead of obtaining an expected flat hydrophobic film, usually a black matrix film with island structures formed thereon is obtained due to variation in the processing recipe, resulting in overflow of color inks and intermixed color inks. Furthermore, the hazardous CF4 gas used in the plasma process is also a grave safety concern.
In addition, another conventional method, disclosed in Japanese Patent Publication No. 09230127, includes coating a 25% C8F17C2H4—Si—(OCH3)3/methanol solution over the substrate and etching using a solution comprising 1% Buffer Fluoric acid (50% HF: 40% NH4F). Thereafter, a color filter layer is formed in the sub-pixel regions. Since the 25% C8F17C2H4—Si—(OCH3)3/methanol solution is coated over the entire substrate, the surface of the substrate in the sub-pixel regions may still have hydrophobic property even though a cleaning process is being performed thereafter, and the problem of intermixing the color inks in adjacent sub-pixel regions still occurs. Besides, the entire process time is longer than 8 hours, and the use of HF acid is of a grave safety concern.